Dec. 1 (UPI) -- Deep beneath New England, a giant mass of warm rock is slowly but steadily rising toward the surface. The revelation undermines some of what scientists thought they understand about plate tectonics and the geology of the mantle.

"The upwelling we detected is like a hot air balloon, and we infer that something is rising up through the deeper part of our planet under New England," researcher Vadim Levin, a geophysicist and professor at Rutgers University-New Brunswick, said in a news release.

The mass of rock is not on the scale of Yellowstone. It measures a couple hundred miles across, and though it may one day form a new volcanic system, it is unlikely to yield an eruption for millions of years.

Scientists were first alerted to something peculiar after noticing a temperature anomaly deep beneath New England.

Levin and his colleagues used seismic data collected by the EarthScope project. For two years, a nation-wide system of seismic sensors, each positioned 46.6 miles apart, measured seismic waves traveling through the continental United States.

Seismic waves can reveal details about the medium through which it's traveling -- in this case, the lithosphere, which includes the upper mantle and crust.

"We're interested in what happens at the interface between tectonic plates -- thick, solid parts that cover our planet -- and material in the upper mantle beneath the plates," Levin said. "We want to see how North America is gliding over the deeper parts of our planet. It is a very large and relatively stable region, but we found an irregular pattern with rather abrupt changes in it."

Earthscope data analyzed by Levin and his partners revealed a mass of rock 300 degrees Celsius warmer than surrounding rock. The seismic observations suggest the upwelling is centered under central Vermont and western New Hampshire.

The unexpected findings -- published this week in the journal Geology -- could force scientists to rethink their models of tectonic plate evolution.

"The Atlantic margin of North America did not experience intense geologic activity for nearly 200 million years," Levin said. "It is now a so-called 'passive margin' -- a region where slow loss of heat within the Earth and erosion by wind and water on the surface are the primary change agents. So we did not expect to find abrupt changes in physical properties beneath this region, and the likely explanation points to a much more dynamic regime underneath this old, geologically quiet area."